In U.S. Pat. No. 5,150,493, issued Sep. 29, 1992, there is disclosed a pipe pig having removable appendages or pins disposed circumferentially around and extending radially outward from the elastomeric body of the pipe pig. While these appendages have proven useful for pipe pigs having a dimension in the order of 10 cm or larger, for pipes having a dimension in the order of 1-2 cm, the pins become awkward to handle and retaining them in the pig becomes difficult.
Pipelines are usually cylindrical and have a central axis. Pipe pigs likewise are usually cylindrical and have a central axis that during use will more or less coincide with the central axis of the pipeline. Scraper elements on a pipeline pig are used to scrape scale off the inside of the pipe and for this reason are usually disposed about the pipeline pig so that they scrape the full inner circumference of the pipe. Examples of prior art scrapers include bristles with bases affixed to a sponge rubber element (U.S. Pat. No. 4,406,031), a spiral blade wound around and extending from a hollow shaft ((U.S. Pat. No. 4,081,875), U-shaped staples embedded in a foamed plastic body (U.S. Pat. No. 4,077,079), several discs extending radially from and concentric to an elongated core (U.S. Pat. No. 3,939,519), pins with anchors extending radially from an elastic cylinder (U.S. Pat. Nos. 4,244,073 and 4,876,761), flexible polyurethane discs of solid construction centrally apertured for mounting on a pipeline pig, the discs having cleaning fingers extending radially from their outer peripheries (United Kingdom patent application no. 2,229,247) and annular sealing lips embedded in shallow annular grooves of an integral elastomeric body (Australian application AU-A-57790/90). These devices tend to be unsuitable for use with small pipes, as for example found in heat exchangers. In particular, the scrapers tend to be complex and expensive.
The inventor has proposed a novel scraper for a pipeline pig. In one embodiment of the invention, the scraper is made from a single metal blank, having a plurality of fins disposed radially about a common central axial member. Each fin includes a scraping end and a connector end. The connector end is connected to the common central axial member, preferably with a portion that is separated from the common central axial member and the scraping end extends circumferentially outward from the connector end. In this manner, the scraping end is cantilevered on the connector end.
Each scraping end preferably forms a quarter circle, and the fins are connected in plural pairs to the common central axial member with adjacent pairs rotationally offset in relation to each other about the common central axial member, preferably about 45.degree. apart so that the scraping ends together cover the circumference of the pipe. In use, the scraper is embedded in an elastic pig body which is placed into and forced through the pipe under hydraulic pressure in known manner.